Industries relating to fermentation feedstock use nearly 100 million tons of carbohydrates annually to produce fuel-grade ethanol and other industrial and commercial products such as monomers for the polymer industry, e.g. lactic acid for the production of polylactide. Millions of tons of carbohydrates are also fermented every year to food and feed products, such as citric acid and lysine. Carbohydrates are attractive as an environmental-friendly substrate since they are obtained from renewable resources, presently, mainly, sucrose from sugar canes and glucose from corn and wheat starches. However, such renewable resources are limited in volume and increased consumption is predicted to increase food costs. There is therefore a need to generate carbohydrates from renewable non-food resources.
An abundant and relatively-low cost carbohydrate source is woody materials, such as wood and co-products of wood processing and residues of processing agricultural products, e.g. corn stover and cobs, sugar cane bagasse and empty fruit bunches from palm oil production. There is also the potential of growing switch grass and other “energy crops” that generate low-cost rapid growing biomass for that purpose. Such biomass contains cellulose, hemicellulose and lignin as the main components and is also referred to as lignocellulose or lignocellulosic material. Such material also contains mineral salts (ashes) and organic compounds, such as tall oils. Cellulose and hemicellulose, which together form 65-80% of lignocellulosic materials, are polysaccharides and their hydrolysis forms carbohydrates suitable for fermentation and chemical conversion to products of interest. Hydrolysis of hemicellulose is relatively easy, but hydrolysis of cellulose, which typically forms more than one half of the polysaccharides content, is difficult due to its crystalline structure.
Despite previous efforts in the field, the known technologies are expensive or industrially unacceptable. Thus, there is a need for alternative and/or lower-cost hydrolysis methods. In addition, carbohydrate costs could be lowered by recognizing the value of and utilizing co-products such as lignin and tall oils. There is therefore a need for a technology that, in addition to using low-cost hydrolysis, generates those co-products at high quality as well as generates carbohydrates that may be converted to ethanol and/or other industrially useful products.